There are a number of assemblies in wind turbine applications which need to be attached to other assemblies or parts of a wind turbine. For example, in direct drive systems for wind turbines, e.g. offshore wind turbines, which use permanent magnet generators, that is, generators where the excitation field is provided by permanent magnets instead of a coil, a number of magnets are arranged in modules. The magnet modules need to be attached to the wind turbine rotor.
The attachment of a magnet module to the rotor may be carried out in different ways. The magnet module may be for example attached to the rotor directly, such as by welding, through bolted connections. The magnet module or even the magnets themselves may be attached to the rotor glued to a rotor body, by stamping the ends of the magnets to hold them in place, attached through the use of clamps coupled to the rotor body or directly to the rotor rim, etc.
One disadvantage with the above ways for attaching the assemblies in a wind turbine is the large amount of welding that is required which is very time consuming and labour intensive.
A further disadvantage is that a large number of bolts are used. In addition, in attachment by gluing reliability is reduced as it is difficult to ensure attachment of the assemblies over time.
In order to at least mitigate the above disadvantage, the above ways for attaching the magnets to a wind turbine rotor have been combined with the use of guide means.
For example, in document US2008093945 the magnets are inserted longitudinally into guide means. The guide means comprise wedge shaped guide grooves that are formed in the rotor. The guide grooves are adapted for receiving the magnets such that they are distributed at the periphery of the rotor and fastened therein. A medium that hardens by a chemical reaction and/or thermal treatment is provided. Such medium is intended for ensuring the attachment of the magnets in the grooves filling the gaps existing therebetween.
Document US2009250935 also discloses the use of guide means comprising grooves that are arranged spaced at regular intervals on the rotor. The grooves have a corresponding trapezoidal shape adapted for receiving trapezoidal shaped magnets. The magnets are attached to the rotor by melting portions of the magnets bonded to the rotor by a high temperature atmosphere.
Document EP2523316 filed by the present applicant discloses a generator rotor having a rotor rim upon which a plurality of permanent magnet modules is arranged extending in an axial direction of the generator rotor. T-shaped anchors are fitted in corresponding grooves that are formed in the wind turbine rotor. Such anchors are provided with bores suitable for accommodating bolts for fixing the anchor to the rotor rim. The permanent magnet modules are inserted between two neighbouring anchors and fixed in place by means of bolts.
The above solutions for attaching different assemblies to each other in a wind turbine have been shown to be reliable and efficient. However, maintenance and repair operations become cumbersome. For example, in the case where the magnets are attached to the wind turbine rotor according to the above disclosed ways, when one or more magnets needs to be replaced, detachment becomes very complicated as bolts are not easily accessible and removal of welding is complex. This hampers maintenance and repair operations rendering them costly. Assembly operations are also complex and time consuming since the bolts are usually locked with glue one by one after they have been completely inserted.
There is thus a need for a mechanism that is capable of providing an easy attachment and detachment of assemblies in wind turbine applications, such as for example for attaching magnet modules to the rotor, as well as parts of the wind turbine stator, such as poles or active part portions of the wind turbine stator.
The present mechanism for attaching two assemblies to each other in wind turbine applications has been developed in order to overcome or at least mitigate the above disclosed disadvantages related to prior art solutions. It has been also found that the present mechanism provides a number of additional advantages as it will be disclosed hereinbelow.